I've been struggling with the exact same problem on Raspberry Pi OS 64Bit all day! I've had to format the sdcard and burn Raspberry Pi OS four times this afternoon.
sudo apt-get autoremove nuked omv the first time by deleting all the files it mistakenly thought weren't needed. sudo apt-get dist-upgrade nuked it the second time and omv-upgrade nuked it a third time. After each time all the files were auto deleted I was unable to reinstall omv without starting from a newly burnt sdcard as the script failed due to missing files. Is there an issue with the raspberry pi script at https://raw.githubusercontent.com/OpenMediaVault-Plugin-Developers/installScript/master/install when using it for 64 bit PiOS?
I tried all that as well and my complete installation was broken. It was just this backports checkmark in the omv-extras settings